This proposal is about the extraction, isolation and characterization of new marine natural products from a series of burrowing sponges such as Anthosizmella varians. Spheciospongia vesparium, Cliona lampa, etc. The extraction and isolation of the different compounds will be performed according to standard lite- rature procedures and the characterization will be performed with the aid of modern instrumentation. We are interested in compounds that are biologically active, i.e., those compounds showing a high degree of cytotoxicity or anti-cancer properties. The biological activity will be assessed in terms of cytotoxicity based on the LD50 for KB cells or anticancer properties initially screened in the P388 lymphocytic leukemia in mice. For the sponge collection and classification we are working in collaboration with Prof. Thomas R. Tosteson from our Marine Station in La Parguera, Puerto Rico and for the testing of the compounds (bioassay) we are in collaboration with Prof. Adriana Baez from our Medical Sciences campus. We are also proposing to undertake a systematic study of important membrane components such as sponge phospholipid fatty acids and sterols due to our initial finding of interesting fatty acids in these sponges. We will also carry out the first comprehensive study of isoprenoid phospholipid fatty acids from marine sponges.